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Penicillins are used to treat infections caused by bacteria. They work by killing the bacteria or preventing their growth.

There are several different kinds of penicillins. Each is used to treat different kinds of infections. One kind of penicillin usually may not be used in place of another. In addition, penicillins are used to treat bacterial infections in many different parts of the body. They are sometimes given with other antibacterial medicines (antibiotics). Some of the penicillins may also be used for other problems as determined by your doctor. However, none of the penicillins will work for colds, flu, or other virus infections.

Penicillins (except bacampicillin tablets, amoxicillin, penicillin V, pivampicillin, and pivmecillinam) are best taken with a full glass (8 ounces) of water on an empty stomach (either 1 hour before or 2 hours after meals) unless otherwise directed by your doctor.

Amoxicillin, penicillin V, pivampicillin, and pivmecillinam may be taken on a full or empty stomach.

The liquid form of amoxicillin may also be taken by itself or mixed with formulas, milk, fruit juice, water, ginger ale, or other cold drinks. If mixed with other liquids, take immediately after mixing. Be sure to drink all the liquid to get the full dose of medicine.

For patients taking bacampicillin:

The liquid form of this medicine is best taken with a full glass (8 ounces) of water on an empty stomach (either 1 hour before or 2 hours after meals) unless otherwise directed by your doctor.

The tablet form of this medicine may be taken on a full or empty stomach.

For patients taking penicillin G by mouth:

Do not drink acidic fruit juices (for example, orange or grapefruit juice) or other acidic beverages within 1 hour of taking penicillin G since this may keep the medicine from working properly.

For patients taking the oral liquid form of penicillins:

This medicine is to be taken by mouth even if it comes in a dropper bottle. If this medicine does not come in a dropper bottle, use a specially marked measuring spoon or other device to measure each dose accurately. The average household teaspoon may not hold the right amount of liquid.

Do not use after the expiration date on the label. The medicine may not work properly after that date. If you have any questions about this, check with your pharmacist.

To help clear up your infection completely, keep taking this medicine for the full time of treatment, even if you begin to feel better after a few days. If you have a ”strep” infection, you should keep taking this medicine for at least 10 days. This is especially important in ”strep” infections. Serious heart problems could develop later if your infection is not cleared up completely. Also, if you stop taking this medicine too soon, your symptoms may return.

This medicine works best when there is a constant amount in the blood or urine. To help keep the amount constant, do not miss any doses. Also, it is best to take the doses at evenly spaced times, day and night . For example, if you are to take four doses a day, the doses should be spaced about 6 hours apart. If this interferes with your sleep or other daily activities, or if you need help in planning the best times to take your medicine, check with your health care professional.

Make certain your health care professional knows if you are on a low-sodium (low-salt) diet. Some of these medicines contain enough sodium to cause problems in some people.

The dose medicines in this class will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of these medicines. If your dose is different, do not change it unless your doctor tells you to do so.

The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.

The number of tablets or teaspoonfuls of suspension that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are taking a penicillin.

Adults, teenagers, and children weighing more than 40 kilograms (kg) (88 pounds)—250 to 500 milligrams (mg) every eight hours or 500 to 875 mg every twelve hours, depending on the type and severity of the infection.

Neonates and infants up to 3 months of age—Dose is based on body weight and must be determined by your doctor. The usual dose is 15 mg per kg (6.8 mg per pound) of body weight or less every twelve hours.

Infants 3 months of age and older and children weighing up to 40 kg (88 lbs.)—Dose is based on body weight and must be determined by your doctor. The usual dose is 6.7 to 13.3 mg per kg (3 to 6 mg per pound) of body weight every eight hours or 12.5 to 22.5 mg per kg (5.7 to 10.2 mg per pound) of body weight every twelve hours.

Adults, teenagers, and children weighing more than 20 kilograms (kg) (44 pounds)—250 to 500 milligrams (mg) every six hours.

Infants and children weighing up to 20 kg (44 pounds)—Dose is based on body weight and must be determined by your doctor. The usual dose is 12.5 to 25 mg per kg (5.7 to 11.4 mg per pound) of body weight every six hours; or 16.7 to 33.3 mg per kg (7.6 to 15 mg per pound) of body weight every eight hours.

For injection dosage form:

Adults, teenagers, and children weighing more than 20 kg (44 pounds)—250 to 500 mg, injected into a vein or muscle every three to six hours.

Infants and children weighing up to 20 kg (44 pounds)—Dose is based on body weight and must be determined by your doctor. The usual dose is 12.5 mg per kg (5.7 mg per pound) of body weight, injected into a vein or muscle every six hours.

For bacampicillin:

For bacterial infections:

For oral dosage forms (oral suspension and tablets):

Adults, teenagers, and children weighing more than 25 kilograms (kg) (55 pounds)—400 to 800 milligrams (mg) every twelve hours.

Children weighing up to 25 kg (55 pounds)—Bacampicillin tablets are not recommended for use in children weighing up to 25 kg (55 pounds). The dose of the oral suspension is based on body weight and must be determined by your doctor. The usual dose is 12.5 to 25 mg per kg (5.7 to 11.4 mg per pound) of body weight every twelve hours.

For carbenicillin:

For bacterial infections:

For oral dosage form (tablets):

Adults and teenagers—500 milligrams (mg) to 1 gram every six hours.

Children—Dose must be determined by your doctor.

For injection dosage form:

Adults and teenagers—Dose is based on body weight and must be determined by your doctor. The usual dose is 50 to 83.3 mg per kilogram (kg) (22.8 to 37.9 mg per pound) of body weight, injected into a vein or muscle every four hours.

Older infants and children—Dose is based on body weight and must be determined by your doctor. The usual dose is 16.7 to 75 mg per kg (7.6 to 34 mg per pound) of body weight, injected into a vein or muscle every four to six hours.

For cloxacillin:

For bacterial infections:

For oral dosage form (capsules and oral solution):

Adults, teenagers, and children weighing more than 20 kilograms (kg) (44 pounds)—250 to 500 milligrams (mg) every six hours.

Infants and children weighing up to 20 kg (44 pounds)—Dose is based on body weight and must be determined by your doctor. The usual dose is 6.25 to 12.5 mg per kg (2.8 to 5.7 mg per pound) of body weight every six hours.

For injection dosage form:

Adults, teenagers, and children weighing more than 20 kg—250 to 500 mg, injected into a vein every six hours.

Infants and children weighing up to 20 kg (44 pounds)—Dose is based on body weight and must be determined by your doctor. The usual dose is 6.25 to 12.5 mg per kg (2.8 to 5.7 mg per pound) of body weight, injected into a vein every six hours.

Adults, teenagers, and children weighing more than 40 kilograms (kg) (88 pounds)—125 to 250 milligrams (mg) every six hours.

Infants and children weighing up to 40 kg (88 pounds)—Dose is based on body weight and must be determined by your doctor. The usual dose is 3.1 to 6.2 mg per kg (1.4 to 2.8 mg per pound) of body weight every six hours.

For flucloxacillin:

For bacterial infections:

For oral dosage form (capsules and oral suspension):

Adults, teenagers, and children more than 12 years of age and weighing more than 40 kilograms (kg) (88 pounds)—250 to 500 milligrams (mg) every six hours.

Children less than 12 years of age and weighing up to 40 kg (88 pounds)—125 to 250 mg every six hours; or 6.25 to 12.5 mg per kg (2.8 to 5.7 mg per pound) of body weight every six hours.

Infants up to 6 months of age—Dose is based on body weight and must be determined by your doctor. The usual dose is 6.25 mg per kg (2.8 mg per pound) of body weight every six hours.

For methicillin:

For bacterial infections:

For injection dosage form:

Adults, teenagers, and children weighing more than 40 kilograms (kg) (88 pounds)—1 gram injected into a muscle every four to six hours; or 1 gram injected into a vein every six hours.

Children weighing up to 40 kg (88 pounds)—Dose is based on body weight and must be determined by your doctor. The usual dose is 25 milligrams (mg) per kg (11.4 mg per pound) of body weight, injected into a vein or muscle every six hours.

For mezlocillin:

For bacterial infections:

For injection dosage form:

Adults and teenagers—Dose is based on body weight and must be determined by your doctor. The usual dose is 33.3 to 87.5 milligrams (mg) per kilogram (kg) (15.1 to 39.8 mg per pound) of body weight, injected into a vein or muscle every four to six hours; or 3 to 4 grams every four to six hours.

Infants over 1 month of age and children up to 12 years of age—Dose is based on body weight and must be determined by your doctor. The usual dose is 50 mg per kg (22.7 mg per pound) of body weight, injected into a vein or muscle every four hours.

For nafcillin:

For bacterial infections:

For oral dosage form (capsules and tablets):

Adults and teenagers—250 milligrams (mg) to 1 gram every four to six hours.

Older infants and children—Dose is based on body weight and must be determined by your doctor. The usual dose is 6.25 to 12.5 mg per kilogram (kg) (2.8 to 5.7 mg per pound) of body weight every six hours.

Newborns—Dose is based on body weight and must be determined by your doctor. The usual dose is 10 mg per kg (4.5 mg per pound) of body weight every six to eight hours.

For injection dosage form:

Adults and teenagers—500 mg to 2 grams injected into a vein or muscle every four to six hours.

Infants and children—Dose is based on body weight and must be determined by your doctor. The usual dose is 10 to 25 mg per kg (4.5 to 11.4 mg per pound) of body weight, injected into a muscle every twelve hours; or 10 to 40 mg per kg (4.5 to 18.2 mg per pound) of body weight, injected into a vein every four to eight hours.

For oxacillin:

For bacterial infections:

For oral dosage form (capsules and oral solution):

Adults, teenagers, and children weighing more than 40 kilograms (kg) (88 pounds)—500 milligrams (mg) to 1 gram every four to six hours.

Children weighing up to 40 kg (88 pounds)—Dose is based on body weight and must be determined by your doctor. The usual dose is 12.5 to 25 mg per kg (5.7 to 11.4 mg per pound) of body weight every six hours.

For injection dosage form:

Adults, teenagers, and children weighing more than 40 kg (88 pounds)—250 mg to 1 gram injected into a vein or muscle every four to six hours.

Children weighing up to 40 kg (88 pounds)—Dose is based on body weight and must be determined by your doctor. The usual dose is 12.5 to 25 mg per kg (5.7 to 11.4 mg per pound) of body weight, injected into a vein or muscle every four to six hours.

Premature infants and newborns—Dose is based on body weight and must be determined by your doctor. The usual dose is 6.25 mg per kg (2.8 mg per pound) of body weight, injected into a vein or muscle every six hours.

For penicillin G:

For bacterial infections:

For oral dosage form (oral solution, oral suspension, and tablets):

Adults and teenagers—200,000 to 500,000 Units (125 to 312 milligrams [mg]) every four to six hours.

Infants and children less than 12 years of age—Dose is based on body weight and must be determined by your doctor. The usual dose is 4167 to 30,000 Units per kilogram (kg) (189 to 13,636 Units per pound) of body weight every four to eight hours.

For benzathine injection dosage form:

Adults and teenagers—1,200,000 to 2,400,000 Units injected into a muscle as a single dose.

Infants and children—300,000 to 1,200,000 Units injected into a muscle as a single dose; or 50,000 Units per kg (22,727 Units per pound) of body weight injected into a muscle as a single dose.

For injection dosage forms (potassium and sodium salts):

Adults and teenagers—1,000,000 to 5,000,000 Units, injected into a vein or muscle every four to six hours.

Older infants and children—Dose is based on body weight and must be determined by your doctor. The usual dose is 8333 to 25,000 Units per kg (3788 to 11,363 Units per pound) of body weight, injected into a vein or muscle every four to six hours.

Premature infants and newborns—Dose is based on body weight and must be determined by your doctor. The usual dose is 30,000 Units per kg (13,636 Units per pound) of body weight, injected into a vein or muscle every twelve hours.

For procaine injection dosage form:

Adults and teenagers—600,000 to 1,200,000 Units injected into a muscle once a day.

Children—Dose is based on body weight and must be determined by your doctor. The usual dose is 50,000 Units per kg (22,727 Units per pound) of body weight, injected into a muscle once a day.

For penicillin V:

For bacterial infections:

For the benzathine salt oral dosage form (oral solution):

Adults and teenagers—200,000 to 500,000 Units every six to eight hours.

Adults and teenagers—125 to 500 milligrams (mg) every six to eight hours.

Children—Dose is based on body weight and must be determined by your doctor. The usual dose is 2.5 to 16.7 mg per kilogram (kg) (1.1 to 7.6 mg per pound) of body weight every four to eight hours.

For piperacillin:

For bacterial infections:

For injection dosage form:

Adults and teenagers—3 to 4 grams, injected into a vein or muscle every four to six hours.

Infants and children—Dose must be determined by your doctor.

For pivampicillin:

For bacterial infections:

For oral dosage form (oral suspension):

Adults, teenagers, and children 10 years of age and older—525 to 1050 milligrams (mg) two times a day.

Children 7 to 10 years of age—350 mg two times a day.

Children 4 to 6 years of age—262.5 mg two times a day.

Children 1 to 3 years of age—175 mg two times a day.

Infants 3 to 12 months of age—Dose is based on body weight and must be determined by your doctor. The usual dose is 20 to 30 mg per kilogram (kg) (9.1 to 13.6 mg per pound) of body weight two times a day.

For oral dosage form (tablets):

Adults, teenagers, and children 10 years of age and older—500 mg to 1 gram two times a day.

Children up to 10 years of age—Dose must be determined by your doctor.

For pivmecillinam:

For bacterial infections:

For oral dosage form (tablets):

Adults, teenagers, and children weighing more than 40 kilograms (kg) (88 pounds)—200 milligrams (mg) two to four times a day for three days.

Children up to 40 kg (88 pounds)—Dose must be determined by your doctor.

For ticarcillin:

For bacterial infections:

For injection dosage form:

Adults, teenagers, and children weighing more than 40 kilograms (kg) (88 pounds)—3 grams injected into a vein every four hours; or 4 grams injected into a vein every six hours.

Children up to 40 kg (88 pounds)—Dose is based on body weight and must be determined by your doctor. The usual dose is 33.3 to 75 milligrams (mg) per kg (15 to 34 mg per pound) of body weight, injected into a vein every four to six hours.

If you miss a dose of this medicine, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not double doses.

Tell your doctor if you have ever had any unusual or allergic reaction to medicines in this group or any other medicines. Also tell your health care professional if you have any other types of allergies, such as to foods dyes, preservatives, or animals. For non-prescription products, read the label or package ingredients carefully.

Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. When you are taking any of these medicines, it is especially important that your healthcare professional know if you are taking any of the medicines listed below. The following interactions have been selected on the basis of their potential significance and are not necessarily all-inclusive.

Using medicines in this class with any of the following medicines is usually not recommended, but may be required in some cases. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.

Certain medicines should not be used at or around the time of eating food or eating certain types of food since interactions may occur. Using alcohol or tobacco with certain medicines may also cause interactions to occur. Discuss with your healthcare professional the use of your medicine with food, alcohol, or tobacco.

Stomach or intestinal disease, history of (especially colitis, including colitis caused by antibiotics)—Patients with a history of stomach or intestinal disease may be more likely to develop colitis while taking penicillins

Check with your doctor if severe diarrhea occurs. Severe diarrhea may be a sign of a serious side effect. Do not take any diarrhea medicine without first checking with your doctor. Diarrhea medicines may make your diarrhea worse or make it last longer.

For mild diarrhea, diarrhea medicine containing kaolin or attapulgite (e.g., Kaopectate tablets, Diasorb) may be taken. However, other kinds of diarrhea medicine should not be taken. They may make your diarrhea worse or make it last longer.

If you have any questions about this or if mild diarrhea continues or gets worse, check with your health care professional.

Oral contraceptives (birth control pills) containing estrogen may not work properly if you take them while you are taking ampicillin, amoxicillin, or penicillin V. Unplanned pregnancies may occur. You should use a different or additional means of birth control while you are taking any of these penicillins. If you have any questions about this, check with your health care professional.

For diabetic patients:

Penicillins may cause false test results with some urine sugar tests. Check with your doctor before changing your diet or the dosage of your diabetes medicine.

Before you have any medical tests, tell the doctor in charge that you are taking this medicine. The results of some tests may be affected by this medicine.

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